Conventional converter circuits comprise a converter unit having a multiplicity of drivable power semiconductor switches which are connected up in a known manner for switching at least two switching voltage levels. On the AC voltage side, the converter unit is connected to an electrical AC voltage supply system. Furthermore, a capacitive energy store is connected to the converter unit, said store conventionally being formed by one or a plurality of capacitors. A drive device is provided for the operation of the converter circuit, said drive device driving the drivable power semiconductor switches by means of a drive signal in method terms during the operation of the converter circuit. The drive signal is typically formed from reference voltages, wherein an assignment unit is provided for forming the drive signal, said assignment unit assigning corresponding drive signal values to the reference voltages. The corresponding reference voltage is the voltage which is set by the converter unit at the associated phase output of the converter unit, and typically corresponds to the associated phase voltage, such that the converter unit sets voltages corresponding to the phase voltages of the electrical AC voltage supply system at its phase outputs. In this case, it is unimportant whether symmetrical or asymmetrical phase voltages are present. Asymmetrical phase voltages are present for example at different phase angles of the phase voltages with respect to one another and/or at different amplitudes of the phase voltages with respect to one another and/or at different frequencies of the phase voltages with respect to one another. In accordance with the prior art, each reference voltage is formed from a constant modulation index assigned to it and a constant modulation angle assigned to it. Consequently, for example in the case of a three-phase electrical AC voltage supply system with three phase voltages, three reference voltages are also necessary and thus also three independent constant modulation indexes and three independent constant modulation angles, wherein these constant modulation indexes and these constant modulation angles are typically formed by calculation, whereby an enormous computational complexity arises. Accordingly, the operation of the converter circuit is very complex, inefficient, expensive and susceptible to faults, whereby the availability of the converter circuit decreases hugely and the maintenance of the converter circuit increases significantly.